Mobile machines, including wheel loaders, bulldozers, motor graders, and other types of heavy equipment, are used for a variety of operations. In order to accomplish these operations, the machines typically include a primary mover, such as an internal combustion engine. The primary mover is often coupled to traction devices to propel the machine and can also power a work implement attached to the machine.
Machines often have a “high-idle” mode of operation. During use of the high-idle mode of operation, an output of the primary mover is generally set to a level sufficient to quickly produce the maximum output to the traction devices and/or work implement. In other words, to ensure that the machine has power sufficient to move the machine and/or work implement under all conditions, the primary mover output (i.e., speed, torque, or a combination of speed and torque) is set at a high level, even if the current operation being performed by the machine demands less than the high output level. Although setting the primary mover output to a high level allows for immediately available power, it may be inefficient and result in excessive fuel consumption, exhaust emissions, and engine noise.
One way to control the output of a primary mover is disclosed in U.S. Pat. No. 4,697,418 (the '418 patent) issued to Okabe et al. on Oct. 6, 1987. The '418 patent relates to a control system for a hydraulic excavator. The excavator has a prime mover, a variable displacement hydraulic pump driven by the prime mover, at least one actuator driven by pressurized fluid from the pump, devices for sensing the operation condition of the actuators, and working elements associated with the actuators. The devices for sensing the operation condition of the actuators include a pressure switch for sensing whether travel motors are in operation and a pressure switch for sensing whether a boom cylinder, an arm cylinder, or a bucket cylinder for driving a front attachment and a swing motor for rotating a swing are in operation. The excavator also has a selection means for selecting an operation mode for each working element. The selection means includes a power mode (P-mode) suitable for heavy digging operations and an economy mode (E-mode) suitable for light digging operations.
Based on the output signals from the sensors and the selection means, the controller selects a combination of a prime mover maximum revolution number and a pump maximum displacement volume (e.g., the controller may select different prime mover and pump settings if digging in power mode versus digging in economy mode). The control means then sets the maximum revolution number of the prime mover and the maximum displacement volume of the hydraulic pump. Setting the prime mover maximum revolution number and pump maximum displacement volume according to the selection means and the operation condition of the actuators may help reduce fuel consumption and noise.
Although the construction machine of the '418 patent may improve fuel efficiency and noise by setting the prime mover maximum revolution number and the pump maximum displacement volume according to the selection means and the operation condition of the actuators, it may still be suboptimal. The control system of the '418 patent may only detect whether the actuators are in operation (i.e., on or off) rather than detecting what the actuators are accomplishing while in operation (i.e., raising the bucket, dumping material, digging, etc.). In other words, the control system of the '418 patent may respond to any operation that activates the pressure switch associated with the front attachments by setting the prime mover maximum revolution number and the pump maximum displacement volume at a level that may be either too high or too low for the actual task being performed. Furthermore, the control system of the '418 patent only controls the operation of the prime mover by setting the maximum revolution number, which may limit the ground speed and thus the productivity of the machine for certain tasks.
The disclosed machine system is directed to overcoming one or more of the problems set forth above.